INTERACTIONS BETWEEN GONADAL HORMONES AND NEURO-VASCULAR RESPONSES TO THE COLD PRESSOR TEST IN YOUNG HEALTHY FEMALES

Previously, we observed divergent vascular responses to the cold pressor test (CPT) among young healthy female participants. This short report examined circulating hormones as contributors to this variability in a larger cohort of female participants. We tested the hypothesis that gonadal hormones would be associated with vascular and muscle sympathetic nerve activity (MSNA) responses to the CPT. CPT responses from 20 young females tested in the early follicular phase of the menstrual cycle or placebo phase of oral contraceptive use were pooled for analyses. Venous blood samples were analyzed (radioimmunoassay; n=18) for circulating total testosterone, 17β-estradiol, progesterone, sex hormone binding globulin (SHBG), and free androgen index (FAI; [total testosterone]/[SHBG]). Mean arterial pressure (MAP; finger photoplethysmography), femoral blood flow (FBF; vascular ultrasound), femoral vascular conductance (FVC; FBF/MAP), and MSNA burst incidence (bursts/100hb; peroneal microneurography), were assessed at baseline and during a hand CPT (3-min). The CPT induced increases in MSNA (baseline: 10±5 vs CPT: 28±12bursts/100hb; P<0.01) and MAP (86±9 vs 96±7mmHg; P<0.01), whereas changes in FVC were not significant (2.6±0.9 vs 3.4±0.6mL/min/mmHg; P=0.89). Neither [17-β-estradiol] (R=0.07; P=0.27) nor [progesterone] (R<0.01, P=0.73) were associated with CPT-induced increases in MSNA, whereas FAI was positively associated with increases in MSNA (R=0.47; P<0.01). Likewise, neither [17β-estradiol] (R=0.11, P=0.65) nor [progesterone] (R=0.01, P=0.98) were associated with percent change in FVC (%FVC). However, there was a negative association between FAI and %FVC (R=0.49, P<0.01). These data suggest that bioavailable testosterone may be associated with CPT-induced increases in MSNA and peripheral vasoconstriction in young healthy females.